Electrical contact



April 20, 1937.

O. S. FIELD ELECTRICAL CONTACT Filed May 24, 1935 FIG. 1.

INVENTO ATTORNEY Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE.

eral Railway Signal Company,

Rochester,

Application May 24, 1935, Serial No. 23,271

9 Claims.

This invention relates in general to electrical contacts, and more particularly to contact fingers for use in trackway apparatus of a railway signalling system.

It is necessary in railway signalling systems to locate the trackway apparatus such as signals and relays comparatively close to railway track, and consequently the vibrations of the track caused by passing trains is transmitted through the ground, especially when the ground is frozen, to this rather sensitive trackway apparatus. This vibration often causes considerable trouble as the frequency of vibration caused by a certain train speed may strike the natural vibration period of certain movable contact fingers and result in a sufficient movement thereof to either falsely close or 'falsely open signalling circuits with possible resulting danger.

In view of the above and other considerations, it is proposed in accordance with the present invention to provide a contact finger for electrical apparatus which is substantially immune to all frequencies of vibrations. More specifically, it is proposed to provide a contact finger having multiple contacting surfaces arranged on the contact fingers in a manner to have different natural Vibration periods, whereby any one frequency of vibration cannot cause an unauthorized movement of all such contacting surfaces.

Other objects, purposes and characteristic features of the present invention will be apparent as the description thereof progresses, during which references will be made to the accompanying drawing, in which:

Fig. 1 is a plan view of a contact finger constructed in accordance with the present invention.

Fig. 2 is a plan View of a modified form of a contact finger also constructed in accordance 40 with the present invention.

45 a relay also illustrating the application of the present invention thereto.

In both Fig. 1 and Fig. 2 of the accompanying drawing, a portion of a contact finger arranged in accordance withthe present invention 50 is illustrated as comprising a flat spring strip S constructed of a suitable metal such as phosphor bronze. The left hand end of this spring strip S is suitably formed for rigidly securing to its actuating means, while the right hand or free end 55 is provided with a piece of contacting metal C such as silver, which contacting metal piece C is fixed thereto by rivets 6 and subsequently soldered.

The present contact finger may of course be applied to many kinds of electrical apparatus, but the necessity for the present arrangement is perhaps most warranted in a light signal mechanism inasmuch as it is not convenient to mount such a mechanism on springs or the like to absorb vibration such as created by a passing railway train. Consequently, the present contact finger has been shown in Fig. 3 as applied to the contact operating mechanism of a color light signal of the type such as disclosed in my prior application Ser. No. 470,056 filed July 23, 1930.

The signal mechanism such as partially illustrated in Fig. 3 includes an operating shaft 8 which is electro-magnetically operated by means not shown herein in either direction from a biased center position for selectively placing one of three differently colored spectacles at the focal point of the light from an incandescent lamp to thereby display various color'light signal indications in accordance with traffic conditions. A crank contact operating means 10 is formed on a portion l2 of the magnetic operating means for the shaft 8 in Fig. 3, which contact operating means I is connected by a pivot pin II to the upper end of a connecting rod M, the lower end of rod l4 having a slot receiving a pivot pin l8 attached to the right hand end of a contact biasing weight IS. The contact biasing weight I6 is pivotably supported at its left hand end by a pin 20 so that a clockwise rotation of shaft 8 obviously produces a counter-clockwise rotation of the contact biasing weight l6 about the pivot pin 20.

Two contact fingers S arranged as shown in either Fig. 1 or Fig. 2 are arranged on opposite sides of a rigid stop strip 22 and assembled by a terminal bolt 24 to an insulating member 26 which is suitably attached to the biasing weight It as shown. The movable contact assembly is shown in a position wherein the contacting piece C of the left hand finger engages a stationary back contact 21, while the contacting piece C of the right hand finger is slightly separated from a stationary adjustable front contact 29, and obviously when the right hand end of the biasing weight It is raised the contacting piece C of the left hand finger will be disengaged from the back contact 27 and the contact piece C of the right hand finger will engage the front contact 29.

In Fig. 4, the contact fingers are assembled in a very similar manner and attached to an armature 28 of a tractive type relay by insulating bolts 30. The relay partially illustrated in Fig. 4 may be of the type fully described in my earlier Patent No. 1,824,129 granted September 22, 1931, or as illustrated, a core 32 of an electro-magnet terminates an enlarged pole piece 34 which attracts the armature 28 pivotably supported by trunnion pins 38 to thereby disengage the contact piece C from the back contact 21 and engage the contact piece C of the upper contact finger with the front contact 29.

In the form of the present contact finger illustrated in Fig. 1 which may be applied to electrical apparatus as just described, a long longitudinal slot 38 is out near one edge and a shorter parallel slot 4i; is out near the other edge, both slots 38 and ill being cut through the contacting piece C and into the flexible strip S as illustrated. In this manner, the contacting piece C is divided into three sections, these sections being carried at ends of parallel portions of the flexible strip S which are of different effective lengths.

It will now be clear that the end of the contact finger in Fig. 1 is thus provided with three multiple contacting surfaces each of which normally engages either the fixed back contact 2! or front contact 29 according to the position of the actuating element, and as these multiple contacting surfaces are carried by different length sections of the spring strip S, these end portions of the contact finger will have relatively different natural vibration periods. Consequently, when vibrations of any frequency are set up by a passing train in the apparatus having this contact arrangement, this frequency cannot strike the natural vibration period of more than one of the end sections of a contact finger, thereby preventing such a degree of movement of all the multiple contact surfaces as can cause an unauthorized change in the condition of electrical circuits controlled thereby.

In the modified form of the present invention shown in Fig. 2, a single diagonal slot 42 is cut from the end at a point near one edge of the contacting piece 0 to a point approximately the same distance from the opposite edge of the spring strip S as shown. In this manner, two multiple contacting surfaces are provided of relatively diiferent mass and carried at the ends of portions of the spring strip S which are also of relatively different flexibility. It is clear that this arrangement in Fig. 2 then provides a contact finger wherein two multiple contacting surfaces each engageable with the same fixed contact have relatively different naturalvibrationperiods, which arrangement acts in the same manner as the form shown in Fig. 1 to prevent any one frequency of vibration from causing undue movement of all the contacting surfaces of the contact finger.

A contact finger for electrical device has thus been provided, wherein a flexible movable contact strip is arranged with a divided end contacting surface so formed that multiple contact making surfaces are provided having relatively different natural vibration periods, whereby to prevent an unauthorized operation of this contact finger by vibration of the electrical apparatus. The present invention obviously has the advantageous feature of employing a single integral finger wherein the above result is obtained by multiple contact making ends so arranged on portions of the end of this finger that, by virtue of their different effective free lengths in one form, provide different natural vibration periods, or in another form this difference is obtained by different size or inertia of the contact making surfaces which are carried by portions of the end' of the contact finger having relatively different flexibility.

The above rather specific description of one form of the present invention is given solely by the way of example, and is not intended, in any manner whatsoever, in a limiting sense. It is also to be understood that various modifications, adaptations, and alterations may be applied to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention, except as limited by the appended claims.

What I claim is:

1. In a circuit controlling device, a contact actuating means, a spring strip operated by the contact actuating means, and contacts on unlike length trifurcations of the spring strip.

2. In a circuit controlling device, a contact actuating means, a spring strip operated by the contact actuating means, and contacts on unlike shaped bifurcations of the spring strip.

3. In a circuit controlling device, a contact actuating means, a spring strip operated by the actuating means, a med contact, and contacts on a trifurcated end of the spring strip engageable with the fixed contact, the trifurcations at the end of the spring strip being of unequal lengths whereby to have different natural vibration periods.

4. In a circuit controlling device, a contact actuating means, a spring strip operated by the actuating means, a fixed contact, and contacts on a bifurcated end of the spring strip engageable with the fixed contact, the bifurcations at the end of the spring strip being of unequal size whereby to have different natural vibration periods.

5. In an electrical device, a contact actuating means, a spring strip carried by the contact actuating means, and a plurality of contact making pieces fixed to differently characterized end portions of the spring strip whereby to have different natural vibration periods.

6. In an electrical device, a contact actuating means, a spring strip extending from the actuating means, and a plurality of contact tips carried on unsymmetrical eXtensions of the spring strip.

'7. In an electrical device, a contact actuating means, a spring strip extending from the actuating means, and a plurality of contact tips carried on differently characterized integral portions of the spring strip.

8. In an electrical device, a contact actuating means, a spring strip extending from the actuating means, and a plurality of contact tips carried on different length portions of the spring strip.

9. In an electrical device, a contact actuating means, a spring strip extending from the actuating means, and a plurality of contact tips carried on diiferent size portions of the spring strip.

OSCAR S. FIELD. 

